what ever happened to jimmy of hoffa? and where did they dump the bold? it's all marked up. tomorrow, they'll bring in the digger to rip it open. >> this is a cold case homicide. >> reporter: it's always been assumed that hoffa, once a powerful president of the teamsters union, who then did jail time for bribery, was killed off by the mob, after he walked out of this detroit restaurant in july 1975. >> i'm going to do what i got to do! >> reporter: it became the stuff of documentaries and movies, like 1992's "hoffa." over the years, many theories and a few leads. an early one, that hoffa's body was entombed in concrete during the construction of giants' stadium, which was knocked down two years ago. later, going on tips, police drained an dug up a backyard pool outside of detroit. three years later, they pulled down a barn in rural michigan. nothing. this latest tip comes from a still anonymous source said to be dying of cancer, who says he saw a body placed here in 1975, as the driveway was being laid. police are not sure what they'll find. >> if it happens to be mr. hoffa,